Answer:
① There are many test methods: many kinds of NMR test methods, including one-dimensional and two-dimensional, have been widely used in structural analysis and material identification; quantitative analysis is no longer limited to 1H NMR experiment, and quantitative analysis of heteronuclear and even two-dimensional NMR appears frequently;
② There are many calibration targets: most compounds have multiple sets of NMR lines, which can be used as calibration targets for quantitative analysis theoretically, which undoubtedly provides convenience for the processing of test data;
③ There are many types of quantitative information: in the literature reports, not only the integral area or intensity of the resonance spectral line is used as the data parameter of NMR quantitative analysis, but also the change value of chemical displacement under specific conditions can be used as the parameter of content determination;
④ There are many reference modes: nuclear magnetic resonance obtains the data information of quantitative analysis through direct comparison of signals. In the experiment, multiple modes such as internal standard, external standard, solvent calibration and physical calibration can be used to provide reference signals. In the determination of relative content, the mode of sample self-standard can also be used.
In a word, NMR is a mature analytical and testing method with distinct technical characteristics, multiple means, flexible methods and rich information, which has a strong competitiveness in drug analysis and identification.
Explanation:
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<span>polar bears, reindeer, and shrubs that live in a single area make up an </span>ecosystem
The correct answer is B. The science of inherited traits
Explanation:
Genetics refers to the field in biology that focuses on studying genes which are the basic units of heredity and therefore the ones that determine inherited traits. Indeed genetic study the way traits are passed through reproduction and also the way genes change over time or express which is closely connected to evolution. Additionally, genetics have been widely studied beginning by the works of Mendel during the 19th century and nowadays the knowledge about genes including the behavior, function, and structure of them is broad. According to this, genetics is defined as the science of inherited traits.
Answer:
As you age, your brain and nervous system go through natural changes. Your brain and spinal cord lose nerve cells and weight (atrophy). Nerve cells may begin to pass messages more slowly than in the past. Waste products can collect in the brain tissue as nerve cells break down.
Explanation:
